The Environmental Protection Agency's new leadership, in a step toward confronting global warming, submitted a finding that will force the White House to decide whether to limit greenhouse gas emissions under the nearly 40-year-old Clean Air Act.

Under that law, EPA's conclusion -- that such emissions are pollutants that endanger the public's health and welfare -- could trigger a broad regulatory process affecting much of the U.S. economy as well as the nation's future environmental trajectory. The agency's finding, which was sent to the White House Office of Management and Budget without fanfare on Friday, also reversed one of the Bush administration's landmark decisions on climate change, and it indicated anew that President Obama's appointees will push to address the issue of warming despite the potential political costs.

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In 2007, the Supreme Court instructed the Bush administration to determine whether greenhouse gases should be regulated under the Clean Air Act, but last July, then-EPA Administrator Stephen L. Johnson announced that the agency would instead seek months of public comment on the threat posed by global-warming pollution.